The effect of chronic hypercortisolemia on substrate metabolism and energy expenditure (EE) has not been well elucidated. This protocol will determine substrate kinetics and EE in patients with Cushing's Syndrome both before and after therapeutic surgery, utilizing stable tracer isotopes and indirect calimetry measurements. This protocol used only CDMAS this year. Dr. Brillon took the Data Management Practicum class that will help him do the final analyses of his data collected on subjects seen in prior years in this subproject.